Journal of Polymer Science Part B: Polymer Physics

Cover image for Vol. 49 Issue 4

15 February 2011

Volume 49, Issue 4

Pages 257–326

  1. Cover Image

    1. Top of page
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    3. Communication
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      Cover Image, Volume 49, Issue 4 (pages i–ii)

      Article first published online: 18 FEB 2011 | DOI: 10.1002/polb.22221

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      Epoxy resins are widely used as adhesives, coatings, paints, composites and in dental therapy, thanks to their impressive adhesion and mechanical properties and chemical resistance. When the resins incorporate mesogenic groups along the main chain and are capable of crosslinking between chains, liquid crystalline domains can be formed. Such resins can also be reinforced with the addition of fillers like carbon nanotubes to improve modulus, strength and toughness, and provide good thermal stability, and thermal and electrical conductivity. On page 301 of this issue, Wei Fang Su and colleagues investigate the effects of the added carbon nanotubes on the curing process of epoxy composites. They find that the nanotubes help to decrease the curing reaction barrier, but that because they also restrict polymer chain movement, the overall degree of cure is lower in the composites than the pure resin.

  2. Communication

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    1. Reverse mode operation polymer dispersed liquid crystal with a positive dielectric anisotropy liquid crystal (pages 257–262)

      Daniela Cupelli, Fiore P. Nicoletta, Giovanni De Filpo, Patrizia Formoso and Giuseppe Chidichimo

      Article first published online: 8 DEC 2010 | DOI: 10.1002/polb.22184

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      Reverse mode operation polymer-dispersed liquid crystals (PDLCs) are transparent in their OFF state and opaque in the ON state. Because of their opaque unpowered states they are ideal for applications in the automobile and building industries, but are limited by the high price and precise properties required of the liquid crystals that are used. A new strategy to prepare reverse mode operation PDLC devices is reported, where doping with liposoluble ionic liquids allows a dc electric field to be ‘built in’. This strategy avoids the pitfalls above and enables OFF state transmittance of up to 75%.

    2. Noncovalent binding interactions of polyacrylamide and clay in nanocomposite hydrogels (pages 263–266)

      Yongtao Wu, Mengge Xia, Qingqing Fan, Yan Zhang, Hao Yu and Meifang Zhu

      Article first published online: 8 DEC 2010 | DOI: 10.1002/polb.22192

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      Conventional chemical cross-linked hydrogels often show limitations in mechanical and swelling behaviors, which limit their applications. Such drawbacks can be overcome by polymer/clay nanocomposite hydrogels. In this investigation, the binding mechanism between the polymer and the clay in these materials is found to be driven by the non-covalent interaction between the amide group in the chains and clay platelets, providing the cross-linking force for the nanocomposite gel network formation.

  3. Full Paper

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    2. Cover Image
    3. Communication
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    1. Toughening of poly(L-lactide)/multiwalled carbon nanotubes nanocomposite with ethylene-co-vinyl acetate (pages 267–276)

      Yunyun Shi, Yanli Li, Jun Wu, Ting Huang, Chen Chen, Ya Peng and Yong Wang

      Article first published online: 9 NOV 2010 | DOI: 10.1002/polb.22177

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      Composites of poly(L-lactide) (PLLA) with carbon nanotubes (MWCNTs) have great thermostability, tensile strength and conductivity, but suffer from a brittleness similar to the unmodified polymer. By adding ethylene-co-vinyl acetate (EVA), here is it shown that the nanocomposites' toughness can be improved. The results show that both the ductility and the impact strength of PLLA/MWCNT nanocomposites are enhanced dramatically, and the associated reduction of tensile strength or modulus can be restored through annealing treatment.

    2. Application of empirical mode decomposition in the field of polymer physics (pages 277–290)

      Shankar Kollengodu-Subramanian, Babji Srinivasan, Jing Zhao, Raghunathan Rengaswamy and Gregory B. McKenna

      Article first published online: 3 JAN 2011 | DOI: 10.1002/polb.22195

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      Empirical mode decomposition (EMD) is an effective digital signal processing technique which can be used to filter time domain data that is corrupted with nonlinear noise. One particular advantage of EMD over other techniques is that besides filtering the noise, it has the ability to provide information about the types of noise affecting the system and, therefore, gives information relevant to improving specific experimental setup/instrumentation.

    3. Dielectric relaxation and conductivity studies on (PEO:LiClO4) polymer electrolyte with added ionic liquid [BMIM][PF6]: Evidence of ion–ion interaction (pages 291–300)

      Sujeet K. Chaurasia, Rajendra K. Singh and S. Chandra

      Article first published online: 2 DEC 2010 | DOI: 10.1002/polb.22182

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      The peculiar behavior of conductivity and dielectric properties change in polymer electrolyte membranes with the addition of ionic liquid (IL) cannot be fully explained on the basis of variation of degree of crystallinity. Here, the concept of contact ion pair formation between IL or salt cations and their associated anions is introduced as a model. Together with the variation in crystallinity, these ion pairs, and the corresponding free ions, are found to be responsible for the transport and relaxation behavior of the system.

    4. Kinetics studies on the accelerated curing of liquid crystalline epoxy resin/multiwalled carbon nanotube nanocomposites (pages 301–309)

      Sharon Chen, Sheng-Hao Hsu, Ming-Chung Wu and Wei Fang Su

      Article first published online: 29 NOV 2010 | DOI: 10.1002/polb.22179

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      Liquid crystalline epoxy resins are promising candidates for self-reinforcing composite materials. Their thermal and mechanical properties are improved by the addition of fillers, which are can also affect the curing process. The curing activation energy and rate of these nanocomposites are found to be strongly dependent on the thermal conductivity of the reinforcing materials used, with conductive carbon nanotubes having a large effect on the curing process as opposed to thermal insulating TiO2 nanorods, which has none.

    5. Phase behavior of polystyrene acrylonitril copolymer and polymethylmethacrylate blends under shear (pages 310–317)

      Abdelkader Berrayah and Ulrich Maschke

      Article first published online: 2 NOV 2010 | DOI: 10.1002/polb.22174

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      In real-life applications polymer materials undergo external stresses such as pressure, mechanical stress, and shear flow. Here the effect of shear on the phase behavior of polymer blends is explained within a new theoretical formalism, which separates the contributions of the thermodynamic behavior of the inactive system and of the excess free energy stored during flow. The latter contribution is found to rely crucially upon variations of the viscosity with temperature, composition and shear rate.

    6. Investigating the effect of nanolayered silicates on blend segmental dynamics and minor component relaxation behavior in poly(ethylene oxide)/poly(methyl methacrylate) miscible blends (pages 318–326)

      Kazem Jeddi, Nader Taheri Qazvini, Seyed Hassan Jafari, Hossein Ali Khonakdar, Javad Seyfi and Uta Reuter

      Article first published online: 19 OCT 2010 | DOI: 10.1002/polb.22168

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      In order to improve understanding of polymer dynamics in layered composites, AC impedance spectroscopy was used to probe the effect of nanolayered silicates on the dynamics of PEO as the minority component in PEO/PMMA miscible blend systems. It is found that various nanoclay loadings have different effects on dynamics in different temperature regions. The results are explained based on the improvement of the confinement effect of PMMA matrix on the PEO chains or the reduction of friction between components.

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